Glare is a common problem in the natural world and in many lighting situations. Sometimes glare is a result of a light source in close physical proximity to an object being viewed. Other times the light source is not physically close to an object but is behind it such that the source is in the same field of view as the object with respect to a viewer. Humans and certain animals have facial shapes and features such as eyebrows that form natural glare shields such that high-angle light (light that forms a high-angle with respect to the horizon) is not visually bothersome. For example, effects of glare are readily observed outdoors early or late on a sunny day. When an observer or photographer faces the Sun the glare may be bothersome and objects may be difficult to view/photograph because of the high contrast between the Sun and the objects, seen on their shadowed sides. When the observer/photographer faces away from the Sun, all objects appear well lit and the observer/photographer does not have to shield or screen his eyes/camera from the direct glare of sunlight.
Light fixtures that primarily direct high-angle light downwardly may not present glare to observers who do not look directly up into the light fixture, but such fixtures may illuminate only small areas. Other light fixtures that direct light into a wide-angle, or low-angle, may illuminate larger areas, but may present glare to observers at a distance. In certain situations, an observer must look at an object that is near a light source, such that light from the light source is likely to be in the observer's field of view.